In the thermoelectric heater/cooler, a plurality of thermoelectric chips of P-type and N-type semiconductors are connected alternately in series with to form a circuit through which a current is fed to heat the one face of the P-type chip and the N-type chip and at the same time to cool the other face of the P-type chip and N-type chip. Conventionally, the chips are cut out from a cylindrical ingot of thermoelectric material. Practically, the chips are made firstly by slicing the cylindrical ingot into a disk and subsequently by cutting the disk along two mutually perpendicular vertical planes. However, since the cylindrical ingot inherently includes some cleavage planes parallel to the direction of crystallization, i.e., perpendicular to the top and bottom of the cylinder, the slicing of the cylinder leads frequently to undesired fracture of the material so that the disk is difficult to be sliced intact from the cylinder. For this reason, the chips have to be obtained from an incomplete disk or fragments thereof. Thus, much waste of material is inevitable to lower the yield factor of the chip production.
In the meanwhile, for enhancing assembly efficiency, it has been proposed to use a bar-shaped thermoelectric element which can be cut into the discrete chips after being mounted on a substrate with an electric circuit for feeding the current to the chips. This mounting technique with the use of the bar-shaped elements is advantageous in that the chips can be mounted to the substrate easier rather than mounting the discrete chips separately; that the chips of the uniform thickness and characteristics can be arranged in good order on the substrate; and that there is less possibility to arrange the chips of P-type and N-type in a wrong order.
However, the bar-shaped elements of uniform length, characteristics and sufficient strength against the cutting are practically impossible to be cut out from the above conventional cylindrical ingot for the above reasons and particularly for that the ingot or the disk cut out therefrom inherently suffers from randomly oriented developments of the cleavage planes. Therefore, it is mostly desired to make such an ingot plate of a layered structure having uniformly oriented cleavage planes that can be successfully cut into the bar-shaped element which is then cut into discrete chips of uniform characteristics.
Japanese Laid-Open Publication (KOKAI) No. 1-202343 discloses a continuous molding of thermoelectric element which might be effective to obtain the ingot plate. However, this method necessitates a very strict control over molten liquid of the material prior to solidification thereof in order to obtain the ingot plate of uniform characteristics. Therefore, it is practically difficult to make ingot plate by this method. Even if the method could provide the ingot plate, the desirable layered structure of uniformly oriented cleavage planes can not be expected.